Water-repellent metal oxide film coated on glass substrate and method of forming same

Abstract

The disclosure relates to a metal oxide film formed on a glass substrate by the sol-gel process using an alcohol solution of at least one metal alkoxide or acetylacetonato. To afford water repellency to the oxide film, carbon fluoride is dispersed in the metal oxide matrix by thermal decomposition of a fluoroalkylsilane compound, e.g. CF 3 (CF 2 ) 3 CH 2 CH 2 Si(OCH 3 ) 3 . An organic polymer, e.g. polyethylene glycol, is dissolved in the metal alkoxide or acetylacetonato solution, and the solution is applied to the glass substrate to form a sol film. By heating at a temperature not higher than 200° C. the sol film turns into a porous gel film. Next, the porous gel film is impregnated with an alcohol solution of the fluoroalkylsilane compound and then heated at a temperature not lower than 500° C. The obtained oxide film is good in durability and abrasion resistance, and on this film the contact angle of water drop becomes greater than 90 degrees.

What is claimed is: 
     
       1. A method of forming a water-repellent metal oxide film on a glass substrate, the method comprising the steps of: applying a first solution, which is a solution of at least one metal oxide precursor selected from the group consisting of metal alkoxides and metal acetylacetonatos and an organic polymer which decomposes at a temperature lower than 200° C. in an alcohol, to the glass substrate to thereby form a sol film on the glass substrate;   heating said sol film at a temperature not lower than 200° C. to thereby decompose and dissipate said organic polymer and converting said sol film into a porous gel film;   applying a second solution which is a solution of a fluoroalkylsilane compound in an alcohol to said porous gel film to thereby impregnate the porous gel with said fluoroalkylsilane compound; and   heating the gel film impregnated with said fluoroalkylsilane compound at a temperature not lower than 500° C.   
     
     
       2. A method according to claim 1, wherein said at least one metal oxide precursor is selected from the group consisting of alkoxides of Si, Ti, Zr and Al and acetylacetonatos of Si, Ti, Zr and Al. 
     
     
       3. A method according to claim 1, wherein said first solution comprises a silicon alkoxide. 
     
     
       4. A method according to claim 3, wherein said first solution further comprises a titanium alkoxide. 
     
     
       5. A method according to claim 3, wherein said first solution further comprises zirconium acetylacetonato. 
     
     
       6. A method according to claim 1, wherein the concentration of said at least one metal oxide precursor in said first solution is in the range from 0.01 to 10 wt %. 
     
     
       7. A method according to claim 6, wherein said concentration is in the range from 0.1 to 5 wt %. 
     
     
       8. A method according to claim 6, wherein the concentration of said organic polymer in said first solution is in the range from 1 to 30 wt % of said at least one metal oxide precursor calculated as metal oxide. 
     
     
       9. A method according to claim 8, wherein said concentration of said organic polymer is not lower than 5 wt %. 
     
     
       10. A method according to claim 8, wherein said organic high molecular material is selected from the group consisting of polyethylene glycol, hydroxypropyl cellulose and polyacrylic acid. 
     
     
       11. A method according to claim 1, wherein said fluoroalkylsilane compound is a fluoroalkyltrimethoxysilane compound selected from the group consisting of CF 3  CH 2  CH 2  Si(OCH 3 ) 3 , CF 3  (CF 2 ) 3  CH 2  CH 2  Si(OCH 3 ) 3 , CF 3  (CF 2 ) 5  CH 2  CH 2  Si(OCH 3 ) 3 , CF 3  (CF 2 ) 7  CH 2  CH 2  Si(OCH 3 ) 3  and CF 3  (CF 2 ) 7  CH 2  CH 2  SiCH 3  (OCH 3 ) 2 , 
     
     
       12. A method according to claim 11, wherein the concentration of said fluoroalkylsilane compound in said second solution is in the range from 0.7 to 5 wt %. 
     
     
       13. A method according to claim 1, wherein said alcohol in said first solution and said alcohol in said second solution are selected from the group consisting of methnol, ethanol, isopropanol and isobutanol.